Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:2.3.3.1 (citrate synthase)
4,488 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The biochemical characteristics of the electron transfer chain are evaluated in purified non-synaptic ("free") mitochondria from the forebrain of 60-week-old rats weekly subjected to peroxidative stress (once, twice, or three times) by the electrophilic prooxidant 2-cyclohexene-1-one. The following parameters are evaluated: (a) content of respiratory components, namely ubiquinone, cytochrome b, cytochrome c1, cytochrome c; (b) specific activity of enzymes, namely citrate synthase, succinate dehydrogenase, rotenone-sensitive NADH: cytochrome c reductase, cytochrome oxidase; (c) concentration of reduced glutathione (GSH). Before the first peroxidative stress induction, the rats are administered for 8 weeks by intraperitoneal injection of vehicle, papaverine, delta-yohimbine, almitrine or hopanthenate. The rats are treated also during the week(s) before the second or third peroxidative stress. The cerebral peroxidative stress induces: (a) initially, a decrease in brain GSH concentration concomitant with a decrease in the mitochondrial activity of cytochrome oxidase of aa3-type (complex IV), without changes in ubiquinone and cytochrome b populations; (b) subsequently, an alteration in the transfer molecule cytochrome c and, finally, in rotenone-sensitive NADH-cytochrome c reductase (complex I) and succinate dehydrogenase (complex II). The selective sensitivity of the chain components to peroxidative stress is supported by the effects of the concomitant subchronic treatment with agents acting at different biochemical steps. In fact, almitrine sets limits to its effects at cytochrome c content and aa3-type cytochrome oxidase activity, while delta-yohimbine sets limits to its effects at the level of tricarboxylic acid cycle (citrate synthase) and/or of intermediary between tricarboxylic acid cycle and complex II (succinate dehydrogenase).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Sequential damage in mitochondrial complexes by peroxidative stress. 166 94

1. The activities of enzymes participating in the regeneration of reduced glutathione (GSH), and their subcellular distribution were studied in cultured rat adrenal cells. 2. It has previously been shown that the adrenocorticolytic agent 7-hydroxymethyl-12-methylbenz[a]anthracene (7-hydroxymethyl-12-MBA) causes a drastic and selective oxidation of mitochondrial GSH in rat adrenal cells. Treatment of the adrenal cells with 7-hydroxymethyl-12-MBA, resulted in a minor decrease in the content of cytochrome c oxidase, nicotinamide nucleotide transhydrogenase, isocitrate dehydrogenase and cytosolic GSH reductase, whereas the activity of lactate dehydrogenase and citrate synthase was unaffected. None of these effects were considered to be responsible for the massive oxidation of mitochondrial GSH induced by 7-hydroxymethyl-12-MBA. 3. 1,3-Bis-(2-chloroethyl)-1-nitrosourea (BCNU) was used to obtain rat adrenal cells cultures with inactivated cytosolic and mitochondrial GSH reductase. The oxidation of mitochondrial GSH, induced by 7-hydroxymethyl-12-MBA, was not dramatically enhanced by the inactivation of GSH reductase, indicating that this enzyme was not rate-limiting in the regeneration of GSH. 4. Fractionation of rat adrenal cells with increasing concentrations of digitonin resulted in an earlier release of citrate synthase in cells treated with 7-hydroxymethyl-12-MBA compared with controls. These results may indicate damage to mitochondrial membranes as a result of 7-hydroxymethyl-12-MBA treatment.
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PMID:Effect of 7-hydroxymethyl-12-methylbenz[a]anthracene and 1,3-bis-(2-chloroethyl)-1-nitrosourea on enzyme activities and oxidation of glutathione in cultured rat adrenal cells. 254 26

The addition of tert-butyl hydroperoxide (t-BuOOH) to isolated mitochondria resulted in oxidation of approximately 80% of the mitochondrial reduced glutathione (GSH) independently of the dose of t-BuOOH (1-5 mM). Concomitant with the oxidation of GSH inside the mitochondria was the formation of GSH-protein mixed disulfides (protein-SSG), with approximately 1% of the mitochondrial protein thiols involved. A dose-dependent rate of GSH recovery was observed, via the reduction of oxidized GSH (GSSG) and a slower reduction of protein-SSG. Although t-BuOOH administration affected the respiratory control ratio, the mitochondria remained coupled and loss of the matrix enzyme, citrate synthase, was not increased over the control and was less than 3% over 60 min. A slow loss of GSH out of the coupled non-treated mitochondria was not increased by t-BuOOH treatment, in fact, a dose-dependent drop of GSH levels occurred in the medium. However, no GSSG was found outside the mitochondria, indicating the necessary involvement of enzymes in the t-BuOOH-induced conversion of GSH to GSSG. The absence of GSSG in the medium also suggests that, unlike the plasma membrane, the mitochondrial membranes do not have the ability to export GSSG as a response to oxidative stress. Our results demonstrate the inability of mitochondria to export GSSG during oxidative stress and may explain the protective role of mitochondrial GSH in cytotoxicity.
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PMID:Retention of oxidized glutathione by isolated rat liver mitochondria during hydroperoxide treatment. 334 2

Using the selective membrane-solubilizing properties of digitonin and a rapid centrifugation method to separate cytoplasmic and mitochondrial components, the metabolic state of mitochondrial glutathione was investigated in isolated rat hepatocytes. Two pools of GSH were released from hepatocytes incubated with increasing concentrations of digitonin. The largest pool (about 85% of cellular total) was released simultaneously with lactate dehydrogenase, the other pool with citrate synthase, indicating cytoplasmic and mitochondrial locations, respectively. The t1/2 of the mitochondrial pool was estimated by linear regression analysis to be 30 +/- 3 h, while the cytoplasmic pool turned over with a t1/2 of about 2 +/- 0.1 h. The rate of incorporation of [35S]methionine or cysteine into the cytoplasmic pool of GSH, when corrected for turnover, was 15 times greater than into the mitochondrial pool. Mitochondrial GSH was not depleted after 60 min with 185 microM diethyl maleate with or without 75 microM bis-1,3-(2-chloroethyl)-1-nitrosourea, a specific inhibitor of glutathione reductase, whereas cytoplasmic levels were reduced to 40% and 10% of control values, respectively. In vivo experiments, using L-(alpha S,5S)-alpha-amino-3-chloro-4,5-dihydro-5-isoxazoleacetic acid to inactive gamma-glutamyl transpeptidase to limit cysteine formation from plasma GSH, demonstrated that in the absence of label reincorporation, liver glutathione exhibits a biphasic turnover. The rates of decay (half-lives) and percentages of total GSH under these conditions correlate well with the half-lives and pool distribution seen in the mitochondrial and cytoplasmic populations of GSH found in the isolated hepatocytes.
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PMID:Status of the mitochondrial pool of glutathione in the isolated hepatocyte. 706 8

The effect of depletion of reduced glutathione (GSH) on brain mitochondrial function and N-acetyl aspartate concentration has been investigated. Using pre-weanling rats, GSH was depleted by L-buthionine sulfoximine administration for up to 10 days. In both whole brain homogenates and purified mitochondrial preparations complex IV (cytochrome c oxidase) activity was decreased, by up to 27%, as a result of this treatment. In addition, after 10 days of GSH depletion, citrate synthase activity was significantly reduced, by 18%, in the purified mitochondrial preparations, but not in whole brain homogenates, suggesting increased leakiness of the mitochondrial membrane. The whole brain N-acetyl aspartate concentration was also significantly depleted at this time point, by 11%. It is concluded that brain GSH is important for the maintenance of optimum mitochondrial function and that prolonged depletion leads also to loss of neuronal integrity. The relevance of these findings to Parkinson's disease and the inborn errors of glutathione metabolism are also discussed.
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PMID:Depletion of brain glutathione is accompanied by impaired mitochondrial function and decreased N-acetyl aspartate concentration. 773 56

Parkinson's disease (PD) is characterized mainly by a loss of nigrostriatal dopamine neurons. Thus far, the actual physiopathology of PD remains uncertain, although recent studies have found decreased activity of complex I, one of the enzymatic units of the mitochondrial respiratory chain, in various tissues of PD patients. Because most, if not all, of PD patients are treated chronically with levodopa, the precursor of dopamine, and because we have shown previously that catecholamines may alter mitochondrial respiration, we assessed the effects of chronic administration of levodopa on complex I activity in rat brain. We found that chronic administration of levodopa, at a dose used in PD patients, caused a significant reduction in complex I activity while it did not affect the activities of complex II, complex IV, and citrate synthase. Reduction in complex I activity correlated well with catecholamine innervation as the reduction was observed mainly in the striatum and substantia nigra and to a lesser extent in the frontal cortex but not in the cerebellum. Moreover, the levodopa-induced decrease of complex I activity was reversible since activities at 1, 3, and 7 days after the last injection showed a progressive return to control values. Incubation of whole brain mitochondria in vitro showed that both levodopa and dopamine inhibit complex I activity in a dose- and time-dependent manner. In contrast, other compounds such as homovanillic acid, 3,4-dihydroxyphenylacetic acid, and 3-O-methyl-dopa were minimally effective. Reduced glutathione, ascorbate, superoxide dismutase, and catalase prevented the effect of levodopa and dopamine on complex I. Various inhibitors of monoamine oxidase also prevented the effect of dopamine.(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Chronic levodopa administration alters cerebral mitochondrial respiratory chain activity. 823 66

Oxygen free radicals have recently been implicated as a major cause of tissue injury in critically ill patients. Glutathione (GSH) is a potent endogenous antioxidant that may be important in minimizing oxidant-induced organ damage. However, this tripeptide is depleted during severe illness. In order to determine the effect of GSH depletion on hepatic high-energy phosphate metabolism, in vivo 31P magnetic resonance spectroscopy was used to measure phosphate ratios in male Wistar rats given 1 ml/kg of diethylmaleate (DEM), an agent that binds and thus depletes tissue GSH, or corn oil vehicle intraperitoneally. Spectra of the liver were obtained in noninjected animals (baseline, n = 15) and in rats 2 and 24 hr after the intraperitoneal injection of DEM (n = 20) or corn oil (control, n = 20). These spectra were used to measure hepatocellular pH, phosphomonoester to ATP (PME/ATP), and phosphodiester to ATP ratios, measures of hepatocellular damage; and the inorganic phosphate (Pi)/ATP ratio, a measure of energy status. In addition, tissue GSH, phosphofructokinase, citrate synthase, and beta-OH-acyl-Co-A dehydrogenase activities as well as hepatocellular ATP were measured in vitro in representative liver samples. Hepatic GSH levels were maximally depressed by 85% 2 hr after the injection of DEM (6.94 +/- 0.34 vs 0.94 +/- 0.22 microM/g wet wt, baseline vs 2 degrees DEM). This was associated with a marked increase in the PME/ATP and Pi/ATP ratios by 25 and 33%, respectively, and both ratios were significantly correlated with the severity of hepatic GSH depletion (r = 0.63, P < 0.001 and r = 0.42, P < 0.01, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)
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PMID:Glutathione depletion alters hepatocellular high-energy phosphate metabolism. 847 34

A total of 300 female broiler chickens were reared from day-old to 10 d of age on the same starter diet. Then they were divided into five groups, receiving a control diet (Group 1) relatively rich in fat (14.3%) and unsaturated fatty acids (87.6%) and standardized with respect to vitamins and minerals, supplemented with 100 mg (Group 2) and 500 mg (Group 4) of RRR-alpha-,gamma-,delta-tocopheryl acetate/kg feed (40.6% alpha-, 41.1% gamma-, 18.3% delta-) or 100 mg (Group 3) and 500 mg (Group 5) all-rac-alpha-tocopheryl acetate/kg feed until slaughter at 6 wk of age. No differences between the supplemented groups were observed with respect to weight gain, feed consumption, packed cell volume (PCV), plasma enzyme activities of creatine kinase (CK) and glutathione peroxidase (GSH-Px), fatty acid composition, and enzyme activities of citrate synthase (CS), and total lactate dehydrogenase (LDH), and 3-OH-acyl-coenzyme A-dehydrogenase (HAD) of breast (Pectoralis major) and thigh (Gastrocnemius interna) muscle. Increasing levels of alpha-, gamma-, and delta-tocopherol were found in blood plasma with increasing dietary levels of these tocopherols. Only alpha-tocopherol was detectable in skeletal muscle and in higher concentrations in thigh than in breast muscle. Hemolysis in vitro and plasma activity of aspartate aminotransferase (ASAT) were lower (P < .01) in Groups 2 and 4 than in Groups 3 and 5. Interactions were observed between dietary type and concentration of tocopherols for plasma CK, GSH-Px, Na+, and K+. No measurable excretion of ethane and pentane was observed in any of the groups. The findings indicate that the oxidative stress in the live animals was minimal. The mixture of natural source RRR-alpha-,gamma-,delta-tocopherols was as efficient in protecting the live chickens as the all-rac-alpha-tocopheryl acetate, when provided on a weight basis as judged from the chosen in vivo parameters of vitamin E status.
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PMID:Supplementation of broiler diets with all-rac-alpha- or a mixture of natural source RRR-alpha-,gamma-,delta-tocopheryl acetate. 1. effect on vitamin E status of broilers in vivo and at slaughter. 882 89

The gene for gamma-glutamylcysteine synthetase (gshA) from Thiobacillus ferrooxidans was isolated from a family of cosmids by its ability to complement an Escherichia coli gshA trxA double mutant which was unable to grow on minimal medium lacking glutathione. The predicted sequence of the gamma-glutamylcysteine synthetase was found to have only 18% amino acid sequence identity to the equivalent enzyme from E. coli. In spite of this low sequence homology, concentrations of GSH in a cell extract prepared from the E. coli gshA trxA mutant containing the cloned gene were almost as high as in a cell extract prepared from a wild-type E. coli strain. The gshA gene was found to be physically and transcriptionally linked to the T. ferrooxidans gene for citrate synthase (gltA). The T. ferrooxidans and E. coli citrate synthases shared 37% amino acid sequence identity and the cloned T. ferrooxidans citrate synthase gene was able to complement an E. coli gltA mutant.
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PMID:The gene for gamma-glutamylcysteine synthetase from Thiobacillus ferrooxidans has low homology to its Escherichia coli equivalent and is linked to the gene for citrate synthase. 882 22

The effects of 8 wk of 35 min of aerobic cycle training (3 times/wk) on indexes of male and female human vastus lateralis muscle antioxidant status were investigated. Training resulted in significant elevations in whole body maximal O2 consumption and muscle citrate synthase activity. Despite this, muscle superoxide dismutase, catalase, and glutathione peroxidase activities were not significantly altered by the training protocol. In addition, training did not affect muscle vitamin E (alpha- and gamma-tocopherol) concentrations. Glutathione status determined as the concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), total glutathione (GSH + 2 x GSSG), and GSH/GSSG ratio was unaffected by the training protocol. There were no significant differences between males and females in any indexes of muscle antioxidant status. These results indicate that the moderate aerobic training typically performed by regularly exercising humans did not positively alter endogenous antioxidant status. This suggests that short-term aerobic training increases capacity for flux through the citric acid cycle without necessarily increasing the ability to handle potential free radicals generated by the enhanced electron flux.
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PMID:Lack of antioxidant adaptation to short-term aerobic training in human muscle. 889 71


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